Understanding child development: Ages 0-3 years

Dr Sara McLean, Australia, August 2020

Resource Summary

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This resource is part of a series from the Emerging Minds: National Workforce Centre for Child Mental Health that outlines the key developmental issues and experiences for children, from birth to age 12. It focuses on the developmental experiences of infants and children aged 0–3 years, providing a brief description of how adverse events may be experienced by a child of this age, and how adults can support a child who has been exposed to disruptive life events.

This resource was written for health professionals. If you are a parent, check out our information about child development for families. Understanding child development: Infants and toddlers describes key developmental experiences in the first three years and ways you can support your baby’s or toddler’s healthy development and wellbeing.

Children develop in the context of their relational and social environment. Since the late 1950s, developmental research has documented the cognitive, social, emotional, and moral development of children in order to better understand their experiences (e.g., Bruner, 1966; Piaget, 1957; Piaget & Cook, 1952; Siegler, Deloache & Eisenberg, 2003; Vygotsky, 1978; Wadsworth, 2004). Although there has been some variety in the way that children’s development has been described, most researchers agree that children typically go through relatively predictable developmental stages, mastering increasingly complex cognitive, social, language, and emotional regulation skills as they age.

A child’s developmental stage will determine how they experience the world, how much they feel they are able to influence their world, and how they make sense of the events that happen to them. It is important for practitioners to understand a child’s developmental journey so that they can respond to children in the ways that are most helpful.

Typical development for children aged 0–3 years

The major developmental task of infants and very young children is the formation of an attachment bond with a caregiver/s who is reliable and responsive to the child’s emotional and physical needs. A baby is completely reliant on their caregiver for survival, and later, for physical and emotional comfort as they explore the world and begin to form beliefs about their capacity to influence those around them. At this age, children are learning to trust their caregiver, as well as their own ability to exert influence on the world.

Children’s attachment experiences are thought to be the foundation for their later social, emotional and cognitive development. A child’s attachment relationship is shaped by how consistently and reliably their caregiver can respond to them when they signal their needs (McLean, 2016). A positive attachment experience is associated with consistent, reliable, and responsive caregiving (Cassidy, 2008). Through experiencing consistent, responsive and predictable care, a young child learns that, through their own actions (such as crying or holding out their arms), they are able to control whether their needs are met (McLean, 2016).

This formative experience gives a young child a sense of their own agency in the world, and of the ‘trustworthiness’ of others – beliefs that become internalised as a ‘working model’ or template. This template in turn forms the basis for the child’s developing self-concept, self-esteem, and emotional, social and cognitive development (DeKlyen & Greenberg, 2008).

Towards the end of this stage of development, a child is beginning to see themselves as a being that is separate from their caregiver, and capable of different thoughts and feelings, although this experience can be fleeting and temporary. Throughout this period of development children remain acutely aware of the emotional state of their primary caregiver, although they will ultimately develop a separate sense of ‘self’.

A basic sense of trust supports a child to engage in learning and exploration outside of their primary attachment relationship, because they are now confident that their caregiver will be there for them when needed. When a child’s attachment has been disturbed or disrupted, it impacts on their willingness and confidence to explore, and therefore affects their social, cognitive, and physical development over time.

The first few years of a child’s life are characterised by rapid physical and cognitive growth and development (Healthwise, 2019). From birth, there is a rapid development in language and communication, as children learn to understand what is being said and what is happening around them. During this period, they go from having very little control over their bodies, to crawling, standing, walking and running.

Children’s reactions to adversity, trauma and loss

Family adversity affects very young children primarily by:

  1. affecting the quality of the caregiver-child relationship; and
  2. reducing the sense of safety and predictability that comes from having familiar surroundings and established routines.

Children at this age are totally reliant on their caregivers for support and survival. Although they do not have the ability to understand or rationalise what is happening, they will be aware that the adults they rely on are emotionally withdrawn or absent. Very young children don’t have the ability to worry about the future, or understand the implications of adversities such as poverty, homelessness, death, etc. for their family. This doesn’t mean they are immune to these events. Infants and young children’s experience of these events is influenced by the impact they have on the adults that care for them. Because young children are absolutely reliant on adults, they are very aware of how responsive and attentive adults are towards them. Although they will not understand why, even young children can be very aware of any changes to adults’ emotional and physical availability. It is this ‘loss’ of adult reliability and responsiveness that is experienced as frightening, rather than the adversity itself.

Most very young children also thrive within a reasonably predictable environment, in which there are familiar daily routines. Periods of adversity, especially those that result in relocation or changes in the family structure, are likely to mean changes to or loss of routines. This can be bewildering for a young child, and they may strongly protest when things don’t go as they’d expected.

Children’s experiences of parental difficulties

Even very young children can sense when a parent is upset and this, in turn, can cause them to become upset. Children are vulnerable to their parents’ understandable feelings of despair, anxiety, and depression during times of adversity. It is important to support parents in order to minimise periods of intense parental distress that can also affect children.

Parents can be less available – physically and emotionally – to children during times of adversity. This can result in children withdrawing from their parents, becoming less interested in exploring their environment and engaging in new learning. It can be helpful to support parents to understand and incorporate child-led activities and play, as much as they are able to.

Exposure to family violence may be particularly frightening for young children, not just because of the violence (typically directed towards the mother), but also because of the impact on their caregiver’s ability to provide a ‘buffer’ against trauma and adversity. Family violence undermines the child’s trust that their caregiver (typically the mother) can protect them from harm.

Signs of distress in children and how they might attempt to cope

During the first few years of life, a child has limited capacity to express their distress in words, particularly using ‘feeling’ words. They are likely to show distress through disruptions in physiological and biological rhythms such as sleep disturbances, nightmares, bedwetting, and loss of previously mastered toileting skills. Very young children may also be prone to more intense tantrums during times of family adversity. These might happen more often when routines are disrupted, when enjoyable activities are cut short, or when they need to wait to be fed, cuddled or put to bed.

How to support children and their families

Times of family adversity, relocation and other transitions can cause considerable disruption to a child’s familiar routines and surroundings. It can be helpful to support the adults in children’s lives to reinstate or establish routines and predictability as soon as possible. This is something that can often be overlooked, as small children are seen as being adaptable and transportable. Working with parents to help them to find new routines that suit their changed circumstances, or times of transition will be important.

Very young children rely on their relationship with their caregivers as a means for making sense of the world, regulating strong emotions, and accessing and extending learning opportunities. Therefore, supporting consistent and responsive care is an important part of supporting infants and young children. It is also important to support caregivers to be able to respond to big emotions and behaviours in a consistent and compassionate way. This helps the very young child to develop the capacity for better self-regulation over time.

There may also be periods during which children may need to live between different locations, or to share their time between parents’ houses. It can help if children have familiar storybooks and toys, including a comfort toy/blanket to take with them as they move between locations.

Resources for parents

Emerging Minds Families has developed fact sheets for parents about child development and ways they can support their child’s healthy development and wellbeing.

Adapted from:

McLean, S (2016). Children’s attachment needs in the context of out-of-home care. CFCA Practitioner Resource. Melbourne: Australian Institute of Family Studies. Available here.
Mclean, S. (2018). Child development milestones: A guide for foster parents. Adelaide: University of South Australia. Available here.
McLean, S (2019). Parenting traumatised children with developmental differences: Strategies to help your child’s sensory processing, language development, executive functioning and challenging behaviours. London: Jessica Kingsley Publishers.


Argus Institute. (2011). Developmental considerations concerning children’s grief. Available here.
Bruner, J. S. (1966). Toward a theory of instruction. Cambridge: Belkapp Press.
Cassidy, J. (2008). The nature of a child’s ties. In J. Cassidy & P. R. Shaver (Eds.), Handbook of Attachment: Theory, Research and Clinical Applications (2nd ed.) (pp. 3–22). New York: Guilford Press.
DeKlyen, M., & Greenberg, M. T. (2008). Attachment and psychopathology in childhood. In J. Cassidy and P. R. Shaver (Eds.). Handbook of Attachment: Theory, Research and Clinical Applications (2nd ed.) (pp. 637–665). New York: Guilford Press.
Healthwise (2019). Growth and development milestones. Available here.
Piaget, J. (1957). Construction of reality in the child. London: Routledge & Kegan Paul.
Piaget, J., & Cook, M. T. (1952). The origins of intelligence in children. New York: International University Press.
Siegler, R. S., DeLoache, J. S., & Eisenberg, N. (2003). How children develop. New York: Worth.
Vygotsky, L. S. (1978). Mind in society: The development of higher psychological processes. Cambridge: Harvard University Press.
Wadsworth, B. J. (2004). Piaget’s theory of cognitive and affective development: Foundations of constructivism. New York: Longman.

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